Housing for semi-conductor rectifier



Aug. 3, 1965 E. KELLER 3,193,875

HOUSING FOR SEMI-CONDUCTOR RECTIFIER Filed April 26, 1963 lb I; 5, 1 I 6a GB '0 7 "1Q,

INVENTOR. Eduard. keLLer 1 m, JW R: PM

United States Patent 3,198,875 HGUSENG FUR SEMi-(IQNDUCTOR RECTlFlER Eduard Keiler, Wettingen, Switzerland, assignor to Aktiengesellschaft Brown, Boveri dz Cie., Baden, Switzerland, :1 join'bstock company Fiied Apr. 26, 1963, Ser. No. 275,968 Ciaiins priority, appiication Switzerland, May 3, 1962, 5,316/62 4 Claims. (Cl. 174- 52) The present invention relates to semiconductor devices such as rectifiers and the like wherein the semiconductor element is constituted by a thin disc of semiconductor material such as silicon.

It is common practice to enclose semiconductor devices of this general type within a housing, and portions of such housing often include glass and metal parts which are fused together. A metal is chosen which has substantially the same coeificient of thermal expansion as the glass, and one such metal which has been widely used is sold under the trade name of Kovar. However, in practice the mechanical strength of such rectifier housings has been found to be insufficient in many cases due to the use of glass which is comparatively fragile. This has been found to be particularly true in cases where the rectifier apparatus is subjected to strong axial and radial acceleration forces, especially in the case where shockloadings occur.

The object of the present invention is to provide an improved construction for housing semiconductor devices in which no glass parts are used. Rather, the housing parts are made entirely from metal and ceramic, and the improved construction has been found to overcome the disadvantage above explained in conjunction with the use of metal-glass parts. In this manner, a substantially greater safety will be attained when the semi-conductor device is subjected to high order mechanical stresses. Moreover, the heretofore used glass-Kovar fusions with their long, step-shaped Kovar parts have led to springy or permanent displacements and twisting of the bolt which passes into the interior of the housing.

Additional displacements can also occur due to temperature factors. The braided stranded copper cable which is customarily used as a flexible intermediate electrical connecting component within the housing cannot always prevent the resulting destruction of the semiconductor disc. In the case of so-called triodes, i.e. a semiconductor rectifier with a control electrode, the conditions are even more adverse due to the presence of the lead from the control electrode.

in accordance with the invention, wherein only metalcerarnic parts are used for its construction, the housing comprises an electrically conductive metal housing part forming a base. Upstanding on this base is a hollow cylinder made from a suitable ceramic such as aluminum oxide, and at the upper end of the cylinder a metallic ring is soldered on, this ring including an inner part which is soldered to and serves to secure a connecting bolt in place which passes downwardly into the housing, Located within and soldered to the inner wall of the ceramic cylinder is a funnel-shaped electrically conductive metallic member, the wall of this member being convergent in the downward direction and terminating in an annular flat terminal base which rests upon the semiconductor disc element. This annular terminal base part of the funnelshaped member also serves to secure in place the lower end of an annular flexible stranded cable, the upper end of this flexible cable being secured to the lower end of the connecting bolt entering the housing from above.

The invention will become more apparent from the following description of one practical embodiment thereof and from the accompanying drawing which illustrates 3,198,875 Patented Aug. 3, 1965 the same. The drawing consists of but a single view of the improved semiconductor housing structure, the view being a central vertical section.

With reference now to the drawing, the housing structure includes a metallic base part 1 made from electrically conductive material such as copper and which is provided with an upper flange part 1a and a lower threaded bolt portion 11) by which the housing can be mounted on a suitable support, not illustrated. Seated on the flange portion 1a of the base is a hollow cylinder 2 which is made from a suitable ceramic material such as aluminum oxide. The lower end of cylinder 2 is soldered to the upper part of a metallic ring-shaped element 3 which surrounds and is in contact with the outer surface of the ceramic cylinder 2, and the lower part of ring 3 which is spaced from the surface of cylinder 2 is in turn soldered to the flange part 1a of the base. A suitable metal for ring 3 is Kovar which has been previously mentioned.

A second ring-shaped metallic member 4, which can also be made from Kovar is located at the upper end of the ceramic cylinder 2. This ring-shaped member 4 includes an outer flanged part 4a which is soldered to the upper end of cylinder 2 and a downwardly and inwardly tapering part 4b which extends downwardly into the in terior of cylinder 2 and is there soldered to the outer surface of a copper connecting bolt 5.

Located within the ceramic cylinder 2 below the funnel-shaped ring part 4b is another funnel-shaped ring 6 which tapers downwardly and inwardly. The upper part 6a of ring 6 is soldered to the interior surface of cylinder 2, and the lower part of ring 6 terminates in an annular base part 611 having a fiat bottom face which rests upon the upper face of the semiconductor disc element 7. This base part 6b is soldered to the upper face of the semiconductor disc 7 to ensure a good current transfer characteristic. Moreover, the annular base part 6b is so configured as to provide an upwardly facing annular groove within which is received and secured the lower end of the annular flexible connecting sleeve or cable 8 made from braided copper strands, the upper end of this annular connecting cable being secured within an annular groove 5a provided in the lower end face of connecting bolt 5. The connections between the braided cable 8 and the bolt 5 and base part 6b of member 6 may be made by clamping, or by soldering, or both.

In the particular embodiment of the invention which has been illustrated, the semiconductor apparatus is of the so-called controlled type. Thus, the semiconductor disc 7 is seen to be provided with a centrally located control electrode 10 to which is connected a lead-in wire 9, the latter passing upwardly through the interior of the annular braided cable 8 and a centrally located bore 5b in connecting bolt 5.

The funnel-shape of ring part 6 will result in a firm connection of the ceramic housing part 2 and the electrical connecting train with the semiconductor disc element 7. The design of ring part 6 is advantageous since it can be manufactured with great precision by punching or pressing. It becomes possible therefore to design a ring part 6 in such manner that it will exert a predetermined pressure upon the semiconductor disc element 7.

Also, the ring part 6 because of its funnel-shaped configuration is well able to absorb tension and compression forces which arise from centrifugal forces as well as shocks. The mass acceleration forces of the heavy copper strands in cable 8 are kept in check, and the semiconductor disc element 7 is relieved from the effects of these forces.

The improved structural arrangement for the housing makes it possible to solder at the same time all soldering points which are located within the housing.

Copper is the most suitable material for the funnelshaped member 6 because its coefficient of thermal expansion is more than twice as large as that for the ceramics which are used, and especially aluminum oxide. In view of the fact that almost no pressure will be exerted on the rectifier disc '7 when the solder hardens, there will occur even a certain tensile stress when it cools ofi" further to room temperature.

During operation of the semiconductor apparatus the improved housing construction results in the advantage that during a rising temperature, the low tensile stress which exists at room temperature will change to a state where mechanical stresses do not exist at all.

I claim:

1. In a semiconductor device, thecombination comprising a metallic housing part forming a base, a semiconductor element in the form of a disc mounted on said base, a hollow cylinder of ceramic material upstanding on said base and secured thereto and surrounding said semiconductor element, a connecting bolt extending downwardly into said ceramic cylinder, a first funnelshaped ring member having a downwardly convergent portion located within said ceramic cylinder, said convergent portion being soldered at its lower end to said connecting bolt and the upper end of said first ring member being soldered to the upper end of said ceramic cylinder thereby to close off the space between said ceramic cylinder and connecting bolt, a second funnel-shaped ring member located within said ceramic cylinder, the upper part of said second funnel-shaped ring being soldered to the inner Wall of said ceramic cylinder and said second ring being convergent in the downward direction and terminating in a flat annular base in electrical contact with the upper face of said semiconductor disc element, and a flexible annular copper cable within said second funnel-shaped ring, the upper end of said annular 4 cable being secured to the lower end of said connecting bolt and the lower end of said annular cable being secured to the base part of said second funnel-shaped ring.

2. A semiconductor device as defined in claim 1 wherein the base part of said second funnel-shaped ring includes an upwardly facing annular groove in which the lower end of said annular cable is received.

3. A semiconductor device as defined in claim 1 wherein the lower end of said connecting bolt includes a downward facing annular groove in which the upper end of said annular cable is received.

4. A semiconductor device as defined in claim 1 wherein the base part of said second funnel-shaped ring and the lower end of said connecting bolt are each provided with an annular groove in which the lower and upper ends of said annular cable are received respectively.

References Cited by the Examiner UNITED STATES PATENTS 2,647,218 7/53 Sorg et al. 220-23 X 2,798,577 7/57 LaForge. 2,960,639 11/60 Tipple 317-235 2,992,372 7/61 Himeon et al. 317234 3,025,436 3/62 Staller 317-234 3,068,382 12/62 Wagner 3l7-234 3,105,926 10/63 Herlet.

FOREIGN PATENTS 1,261,798 4/61 France. 1,087,706 8/60 Germany.

714,976 9/54 Great Britain.

DARRELL L. CLAY, Primary Examiner.

JOHN P. WILDMAN, Examiner. 

1. IN A SEMICONDUCTOR DEVICE, THE COMBINATION COMPRISING A METALLIC HOUSING PART FORMING A BASE, A SEMICONDUCTOR ELEMENT IN THE FORM OF A DISC MOUNTED ON SAID BASE, A HOLLOW CYLINDER OF CERAMIC MATERIAL UPSTANDING ON SAID BASE AND SECURED THERETO AND SURROUNDING SAID SEMICONDUCTOR ELEMENT, A CONNECTING BOLT EXTENDING DOWNWARDLY INTO SAID CERAMIC CYLINDER, A FIRST FUNNELSHAPED RING MEMBER HAVING A DOWNWARDLY CONVERGENT PORTION LOCATED WITHIN SAID CERAMIC CYLINDER, SAID CONVERGENT PORTION BEING SOLDERED AT ITS LOWER END TO SAID CONNECTING BOLT AND THE UPPER END OF SAID FIRST RING MEMBER BEING SOLDERED TO THE UPPER END OF SAID CYLINDDER THEREBY TO CLOSE OFF THE SPACE BETWEEN SAID CERAMIC CYLINDER AND CONNECTING BOLT, A SECOND FUNNEL-SHAPED RING MEMBER LOCATED WITHIN SAID CERAMIC CYLINDER, THE UPPER PART OF SAID SECOND FUNNEL-SHAPED RING BEING SOLDERED TO THE INNER WALL OF SAID CERAMIC CYLINDER AND SAID SECOND RING BEING CONVERGENT IN THE DOWNWARD DIRECTION AND TERMINATING IN A FLAT ANNULAR BASE IN ELECTRICAL CONTACT WITH THE UPPER FACE OF SAID SEMICONDUCTOR DISC ELEMENT, AND A FLEXIBLE ANNUAL COPPER CABLE WITH SAID SECOND FUNNEL-SHAPED RING, THE UPPER END OF SAID ANNULAR 